Transformer



Aug. 5, 1947.

' grmsromlan Filed April 10, 1943 VI. W

BLOWfR F EDMONDS I W' "1 7". l

R Sheets-Sheet 1 INVENTOR. I'M/VA M Amm F. \MEDMONDS Aug. 5, 1947.

mansrom 2 Shaw-Shut 2 Filed April 10 UNITED 2,424,913

I rmsroma' Frank w. sumac, a. s. x..- was -to. Federal"1' Ielephone A: Radio New York..N.' 1., a corporation of Application April 10, 194:, sci' lai'iva iszaes '14 ClalnmiCL 175-462)} This invention relates to transformers and particularly to transformer windings adapted for improved operation when carrying substantial currents.

A principal purpose is to provide a substantially lighter transformer construction, the'preferred form being especially suitable for use'in aircraft in which reduced weight is of primary, importance. Further purposes are to improve heat radiation from the winding, to reduce materially the copper loss, and the provision of an improved supporting bracket structure. h

Other objects and advantages will appear from the following descriptionconsidered in connection with the accompanying drawings, in which Fig. 1 is a side elevation of a transformer'embodying the invention;

Fig. 2 is a plan view thereof;

Fig. 3 is a'vertical section "through a onlineHofFigJ; '1,

Fig. 4 is a vertical section'on line 4-4 of Fig. 2; and" Fig. 5 is an enlarged. fragmentary yie'w of an end of the coil;

winding The invention is illustrated in connection with t a step-down transformer having three coils C mounted on a core A formedof two E type halves suitably held together, as by a metal clamping band l0 fastened by clips l'l. Suitable mounting brackets are provided, and'an improved construction is shown which gives the solidity of support with a minimum of weight, together with ease of assembly. In this arrangement four brackets I! are provided, each extending transversely across a corner of' the core A and-bein constructed of metal angle sectionshaving suitable mounting lugs l2a soldered to the end portions of each bracket. The brackets I; are all held firmly in place on the core .A by a clamping band ll of suitable metal such as steel; which is placed under tension and held in by 'clip ll, said band and clip being advantageously similar to those customarily employed in fastening cases and the like. The band is advantageously stretched to a point below its elasticlimit, permittlng expansion and contraction mation or loss of tension.

Each bracket 1: is' advantageously provided v with inwardly extending retaining lugs lib attached as by soldering to the inner edges of the" without deforobiectionablereaction-iwith the iron of the core,

suitableinsulationsuch asa sheet of glass cloth be interposed between each bracket l2 and theadiacent portion ofcore A.

- The coil'siC .areid'entical .in construction, so only one 0011- will be' described. 'It is mounted on winding tube. I"! ofusual type, held in place on the core A- by wedges W' which maybe formed from suitable insulating material; The coil comprises an inner primary winding of rectangular copperwire, the successivelayers l6 of' the wire 1 and adjacent turns of the wirebeing suitably in-. sulated. I For this purposethe wire may be cov- 1 ered withwgla'ss fabric orotherinsulation, and

successive layers of the winding may be sepaeach other as hereinafter set forth. In the illustraflted embodiment there are'flve layers It in the primary winding."

. The secondary winding-*consistsof a plurality I of turns formed from-a strip of sheet metal which ordinarily 'willbe equal in width to the rimary layers", andjwhich preferably-is formed from extremely-thin sheet-metal such as copper, a strip of onzi'ey ncnthick and 2% inches wide having been used effectively in a transformer embodying 'the inventiomf The portions of successive turns ll'whichlie aaginst each other are separated by suitablei insulation, which may advantageously consist orglass cloth strips n. In'the form illustrated-the secondary winding-consists of six turns.

'Ih'e-transformer-is designed to carry relatively high current-,especially in the secondary, which necessarily, resultsiin a-substantial tendency toward heating. Inorderto improve the radiation ofheat'frohi. the-"windings, the portions thereof located at oppositesides of the core A are provided withair ducts" extendingbetween adiacent layers ll ofgthe primary and between turns ll of-the secondary; Each duct 20 is formed by the insertion of spacers 2| extending parallel to p i the winding axis advantageously located ad- Jac'ent ends of the straightmnszof said layers I and tumslthat li'ezparallel to theaides of the core A. Spacers 2| are formed of suitable material }having necessary insulatinm m echaalcal and 'dielectric properties. For-thiamine a material made up or superposedsheets of glass cloth consolidated by a binder which is highlyreaistant to temperature changes has been found especially suitable, a commercial form ofthis material being dcflg ated by the trade-mark FF-lO (Formica) amass stantially simpler than prior arrangements in which the brackets were attached to the core by of the tube. and a plurality or spacing memhers extending lengthwise of said tube between contiguous winding layers with at least "some of the spacing members being formed of conducting a material and forming lead-in 'conducto'rsfor the winding layers and extending lengthwise through the length of the coil and with the spacing memwhich serves as a path for the magnetic "flux is not interrupted or ailected by bolts, screws or other projections made of metal having entirely different characteristics. when the brackets are made of a metal which might interact chemically or otherwise with the registeringportions of the material wound around saidtube and extending core. particularly when moisture is present. the disclosed type of mounting is furthermore advan tageous since it facilitates the use of asimple inbars forming open-ended'cooling air-ducts intermediate the' spacing members and between the not surfac s or the sheet metal; g

'i. A tra'nsform'er coil construction comprising, a winding tube, a' plurality of winding layers formedof a strip fr substantially flat conducting lengthwise thereof, a plurality oi spacing inem-s bers positioned in two groups which groups are sulating element between each bracket and the core, made of material which is suitable for the prevention of any such electrolytic or other action, an arrangement that is' diiflcult to provide where the brackets are attached by the usual fastening means.

spaced arcuately with respecttq thecentral axis of the tube with "the spacing members in each While a specific embodiment of the invention has been disclosed, this is'intended to be illustrative rather than restrictive, the scope of the invention being indicated in the claims.

What is claimed is:

1. A transformer construction comprising a core, cooperating induction coils mounted on said core, a bracket construction for supporting said core bearing against the core, and a retainin! band extending around the bracket construction and core under tension, arranged to hold said core in place against said bracket construction.

2. A transformer construction as setforth in claim 1, in which the band is formed of metal and is under tension below its elastic limit, arranged topermit expansion of the core and stretching of the hand without permanent deformation of said band. I

3. A transformer construction comprising a generally flat core, induction coils mounted on said core, a bracket for supporting the core extending transversely thereto. means for clamping the bracket against the surface of the core. and retaining means on the bracket engaging opposite sides of the core arranged to prevent movement of the core with respect to the bracket.

4. A transformer construction comprising a core of ferrous metal, induction coils mounted on said core, a supporting bracket of non-ferrous metal, an insulating element located between the bracket and the core, and strap means for holding the core in position on the bracket bearing against said insulating element.

5. In a transformer coil construction. a win ing tube, a plurality of winding layers formed of group being par'allel'to eachfo'ther and radially disposed with the ends oi'the spacing members A projecting beyond the ends oi' the' coil' and with each spacing'member being positioned between contiguous winding layers, the'two groups of spacingmembers thus cooperating to forms. plurality of'parallel open-endedcoolingducts, and a plurality of clamping devices mounted on said winding tube and'each engaging thefadiacent by' the spacing members relationship. I

ends of onegroup of the spacing members where- I are held rigid ii xed 8; In a transformer construction, 'the'combination of, a winding form,agpluralityof'winding layers formed of a strip of substantiallyfilati onducting material wound around said iorm'and extending lengthwise thereof, s urs ity or spacing members positioned in two groups which groups are spaced arcuately' with respectftothe I central axis or the winding form with-the spacing members in each group being parallel to each other and radially disposed withres'pect to said axis and with each spacing member being positioned between contiguous 'wihdl nslayers, the

' two groups of spacing'membersthus cooperating to forma plurality of parallel open' -ended cooling ducts, and insulating means separatingfsaid winding layers in zones arcuatelyspaced from said 'air-ducts with the strip or conducting mete- -insulating means a strip of thin sheet metal wcumlv said tube with the width of the strip extending'length' wise of the tube, and a plurality of spacmg meman open-ended cooling air-duct intermediate the] spacing members and between the flat surfaces of the winding layers, and with the sheet metal rial being secured at it and 'held-"taut throughout by. the cooperatiye action of' friction on the strip by said spacing mem i's-a 'id said 9., In a transformer construction, "the tion of.- a core having a leg, ga'winding form on said leg of rectangular cross section; apluraiity of winding layers i'crmed of a strip of conducting material wound-around said form with each winding layer having two pairs of parallel sides which extend along. therespective sides of said form,

H [a pluralityjfo ispacing members, positioned in four bers extending lengthwise of said tube v gtoups-fwhiaghhmliboeitioned respectively at the M c Iormwithihe spacing memupbeing-"parallel to eachfother the sides of the' winding layers and with each spacing member beingpositioned between contiguous wlnding1layers;,.thespacing members bebeing bent around a portion of the spacing members at the edges of the air-duct thereby to assist in maintaining tension on the sheet metal at the air-duct. i u

6. In a transformer coil construction, a winding tube, a plurality of winding layers formed of ingso disposed thatv with the winding layers I stretched tightly around them a plurality of parallel open-ended cooling ducts are formed, said contiguous winding layers forming air ducts along two opposite sides cf'the winding form while the winding layers are heldin close proximity along the other two sides. and insulating means between the winding layers along said other two sides.

10. In a transformer, the combination of, a core be the z ne of intersection of construction having a leg with an intent opening; and a winding assembly comprising. insulating means surrounding said leg, a coil a-embly iormed by a plurality of winding ml 'mmd around said leg with the layers insulated from each other by said insulating means only through said opening and with the layers being spaced from each other thereby to provide open ducts between the layers exteriorly of said winding space, a plurality of elongated rigid spacing members mounted in used parallel relationship parallel to and spaced from said leg each spacing memher being between contiguous winding layers thereby to maintain the layers in said spaced relationship.

ii. In a polyphase transioriner, the combination oi, a core construction having three parallel legs with winding space between the legs. a winding assembly including a winding wound on each v of said legs, each of the windings being iormed by single-turn layers iormed by a strip oi thin sheet metal the width of which is equal to the length 0! the coils, and a plurality o! spacing members holding the layers of said windings in taut spaced condition with the two ends of each winding secured to the adjacent spacing members and with said adjacent spacing members providing the electrical connections to the windings.

12. In a three-phase transformer, the combination oi, a core built up of E-shaped laminations and having three legs with two openings between the legs, a strip of sheet metal holding said core in iixed relationship, a winding assembly formed by rimary and secondary windings on each oi said legs. certain of said windings being formed by strips of sheet metal wound tightly and held taut, a plurality of spacing members positioned in spaced relationship between the layers of said windings and holding said windings separated exteriorly of said openings between said legs whereby air ducts are provided. and insulation means iilling the space between v the layers oi the winding within said openings; I

13. In a transformer, the combination 0!. score having a plurality oi legs separated by an opening; and a winding assembly comprising. a wind-;

ing shell'surrounding one of said legs andextending through said opening adjacent saidleg 8 oithelemapairoiradiallydisposed arallel osts iai lycarriedbysaidshellandspacedaaially withrespecttotheasisottheleg. rality oi spacers carried by said whereby air ducts are provided between the coil 14. Inanair-cooled transformer theeombinationotacoreassembbhavingan ing layers positioned within said opening intermediatethewindinglayersandiormingwiththe windinglsyersacompactassemblzsaidwindmg assemblyinciudingapluraiityotinsuiatingmembers positioned outside said opening and holding said winding layers in rigid spaced relationship thereby forming air ducts between the winding layerswiththewindingiayersbeingheldtaut by the cooperative action of the insulating layers within said opening and the insulating members.

FRANK W. EDMON'N.

REFERENCES CITED The ioilowlng reierencesareoi recordinthe ilie of this patent:

UNI'I'ED STATE PATENTS Number Name Date 604,673 Bchwedtmann liar. 4, 1002 1,062,046 Smith (A) Kay 20, 1013 1,427,783 Burke Sept. 6. 1922 1,535,094 Bingay Apr. 28. ms 1,641,272 Horelick Sept. 0, 1m 1,666,885 Smith (3) Oct. 6. 1926 1,747,953 Roothan Feb. 18, 1930 1,686,268 Wilkinson July 10, 182'! 1,900,729 Rigante Apr. 2, 1935 7 1,833,818 Lennox Jan. 13, I025 1.503.366 Ibrtescue Dec. 1, 1026 Y 1.108;! Hopkins Mar. 5, i929 FOREIGN PATENTS Number Country Date 466,619 Great Britain May 11, 1937 369,983

with the axis oi the shell concentric with the ads Great Rb. 2. 1928 

